Electrical fluid heater



May 24, 1949. CHAPMAN 2,471,260

ELECTRICAL FLUID HEATER Filed Jan. 30, 1947 2 Sheets-Sheet l r .9 j i:A? F1G-.l.

I 4 ii i awe/whom HAROLD P. HAPMAN May 24, 1949. H. P. CHAPMANELECTRICAL FLUID HEATER 2 Sheets-Sheet 2 Filed Jan. 50, 1947 HAROLD P.CHAPMAN yaw-2 W ELM Patented May 24, 1949 UNITED STATES PATENT OFFICEELECTRICAL FLUID HEATER 'Harold P. Chapman, Columbus, Ohio, assignor ofone-half to Eli F. Margold, London, Ohio Application January 30, 1947,Serial No. 725,316

7 Claims. 1

This invention relates to an improved electrically heated receptacle,and has particular reference to a receptacle for heating water, andother fluids, to predetermined temperatures and for maintaining thefluids within a narrow predetermined temperature range.

In laboratory apparatus, such as that used by dentists and dentaltechnicians, it is often desirable to heat impression-forming wax whichis to be placed in the mouth of a patient to selected temperaturesadapted to render the wax plastic but not so highly heated as to causeundue discomfort to the patient.

Accordingly, the present invention provides apparatus embodying aliquid-holding receptacle having an open top and wherein a removableelectrically controlled heating unit is adapted to be positioned in thereceptacle and immersed in the fluid contained therein to heat the fluidto required temperatures.

It is another object of the invention to provide an electricallyactuated heating unit for liquid-holding receptacles and wherein theheating unit is freely removable from the receptacle so that the lattermay be readily kept in a cleanly and sanitary condition, the heatingunit being so formed as to constitute, when applied to the receptacle, acomponent part of the handle structure of the receptacle, so that thelatter may be readily carried from place to place with the heating unitin its operative position.

It is a further object of the invention to provide an electricallyactuated heating unit for liquid-holding receptacles in which theheating unit includes a depending heat-sensitive tube arrangedvertically within and adjacent to one side of the receptacle, therebeing arranged in parallel relationship with and adjacent to theopposite sides of the tube the vertical legs of a resistor element, sothat in operation the heat radiated from and conducted by the resistorcontaining legs will be directly transmitted to the heat sensitive tubeand a thermostatic switch arranged in said tube may functioneffectively, automatically and within a closely controlled temperaturerange to open or close the circuit employed in transmitting electricalcurrent to the heat-generatin resistor of said legs.

A further object resides in a heating element of the character specifiedwherein manually actuated adjustable means are provided for causing theactuation of the thermostatic switch to open or close the resistorcircuit at any desired temperature within a predetermined range.

A still further object is to provide a heater of this nature employing asignal lamp in the resistor circuit, which lamp is automaticallyenergized when the resistor circuit is closed by the thermostatic switchcontrol, so that the user of the appliance will be provided with avisual signal for determining when the resistors are being energized.

Still a further object is to provide an electrically actuated heatingelement of the character set forth wherein the verticalresistor-containing tubes are directly united with the interposed casingof the thermostatic switch by a plurality of heat-conducting lugs, sothat the heat of the resistor tubes will be conducted directly to thewalls of the switch casing, as well as being radiated thereto, wherebyto render the operation of the thermostatic switch extremely sensitivein response to temperature variations of the resistors.

The present application constitutes a continuation-in-part of my priorapplication, Serial No. 539,044 filed June '7, 1944.

For a further understanding of the invention, reference is to be had tothe following description and the accompanying drawings, wherein:

Fig. 1 is a side elevational view of a liquid receptacle provided withthe electrical heating unit constituting the present invention;

Fig. 2 is an enlarged vertical sectional view taken through thereceptacle and its associated heating unit;

Fig. 3 is a vertical transverse sectional view on the plane indicated bythe line 3-3 of Fig. 2;

Fig. 4 is a top plan view of the manually adjustable control for theheating unit;

Fig. 5 is a horizontal sectional view on the line 5--5 of Fig. 2;

Fig. 6 is a similar view on the line B6 of Fig. 2, illustrating theheating unit on a larger scale;

Fig. 7 is a diagrammatic view disclosing the electrical circuit of theheating unit and its associated parts.

Referring more particularly to the drawings, the numeral I designates areceptacle which has been especially designed to receive the electricalheating unit indicated generally at E. The receptacle preferablycomprises a cylindrical outer casing 2 having rolled flanges 3 and 4 atits upper and lower edges, respectively, the casing being open at thetop and bottom thereof, as shown in Fig. 2. Positioned within the casingis a removable liquid-holding receptacle 5, the latter having a bottom6, and a cylindrical side wall l which is spaced from the wall of thecasing 2, the upper edge of the side wall I terminating in an outwardlyrolled flange 8 which rests on the flange 3 of the casing, so that thereceptacle 5 is removably suspended within the outer casing. The bottom6 of the receptacle is located in a horizontal plane above the flange 4of the casing, so that when the receptacle becomes heated, it will notinjure the underlying base. The open top of the receptacle 5 is adaptedto be covered by means of a removable lid a which is recessed as at itto receive the heating unit E. Exteriorly, the casing 2 is provided witha fixed handle, shown at H.

The heating unit E comprises a casing l2 which is disposed, in the main,exteriorly-oi the receptacle parts when the heating unit isactivelypositioned. The casing involves a vertical tube 13 which is adapted tobe positioned immediately adjacent to the handle I I, so that when theha--- dle is grasped by a user, the tube l3 will be simultaneouslygrasped by one hand of the user, so that the receptacle may be liftedand transported without disturbing. the operating position of theheating unit. Positioned in the lower end of the tube 13 is a terminalblock M' provided with spaced depending prongs l5 adapted for detachableunion with a current-supplying socket It. Also, arranged within the tubeI3 is an incandescent lamp H, which is energized when the heating unitis in active operation. The upper end of the tube [31s closed by meansof a colored glass lens [8, which .is illuminated by the lamp H toapprise the operator of the apparatus when the heating unit is inoperation.

Forming a part of the casing l2 and joined with the upper portion ofthe. tube t3is a horizontally disposed tubular section [9, whichis'adapted to extend over the top of the handle ll and one side of thereceptacle 5. Abuttl'ng the inner end of the tubular section [9 is ahead20, the latter being united unitarily with the tube l3 and the sectionl9 by means of one-or more tie bolts 2! disposed within the confinesofthe'section 19. Depending vertically from the lower central portion ofthe head 20 is a tubular switch casing 22 in which is removablypositioned aihollow member 23 containing a thermostaticcircuit-controlling switch S.

Also carried by the head 'Mlare depending. resistor-holding tubes 24,which are located on opposite sides of the switch casing 22in adjacentrelationship therewith. The tubes 24 are directly united with thewallsof thecasing 22 by means of the heat-transmitting lugs: shownat'25inFig. 3. The lower endsof thetubes 24 terminate in an integralU-shaped. horizontally disposed tube 25. Positioned in the tube sections24 and 26 is a heat-generating resistor 21, one :end ofwhich beingconnected by a conductor 28 with oneof the block terminals l5, while theother end of the resistor is connected withxthepontact element as of theswitch S.

As shown more particularly in Figs. 2 and 7, the switch S comprises apair of bowed, oppositely facing..metallic strips ill, the latter beingformed from a metal possessinga difierent coefiicient of. expansion thanthe metal comprising the wall of the member 23. At their nearestadjacent points, the strips are provided, intermediately of theirlengths, with the "contact elements shown at 29 and 3| which, whenin'relative engagement, are adapted to complete the electrical circuitused in energizing the resistor 21, and when relatively separated tointerrupt/or open said circuit.

, Thus, the lower ends of the strips 30 are semember 23,, while theupper ends of said strips are connected to a transversely extending web32, the latter having its axial portion swiveled to the lower end of anadjusting screw 33. This screw extends upwardly through the head 283 ofthe casing i2 and is fixed to a temperature graduated and indicatingwheel 34, the threaded shank of the screw being received in aninternally threaded bore s5 provided at. the top of the member 23. twill be seen that when the wheel or knob 3A is rotated, verticalmovement will be imparted to the screw 33 and the web 32. If thismovement is downward, the strips 39 are bowed in a direction to bringthe contacts 29 and 3! toward each other, and, if in an upwarddirection, such movement will impart tensioning forces to the strips toeffect relative separation of contact elements. In this manner, theoperating positions of the strips 30 may be controlled to producecircuit completion and opening at various temperatures. The contact 3!is joined by a conductor 35 with the lamp l1 and one of the terminalprongs 15.

The interior of the receptacle 5 may be provided with a supporting rack31 to be heated for the reception of various materials or utensils inwhich such materials are placed within the receptacle. Such utensils mayreceive an impression-forming wax employed by dentists in reproducingthe contours of a patients mouth and teeth. The receptacle 5 is adaptedto receive a suitable supply of water, and heat is transmitted to thewater by the energization of the resistor 2i and thence to the material,not shown, posi tioned on the rack 3 and the contents thereof. Thecasing l2 may be provided with a well 38 adapted for the removablereception of a mercury column thermometer 3d, which may be employed forchecking the adjustment and calibration aiforded by the wheel or knob 3dof the switch. When the thermometer occupies the well 38, the lower endthereof will be immersed in a body of Water contained within the innerpan or receptacle 5.

By reason of the heat conducting relationship which the resistor tubes24 bear to the switch casing 22, the heating unit is particularlysensitive to temperature fluctuations. In normal operation, the switchfluctuates Within a range of one degree Fahr. plus or minus from thetemperature at which the switch is set to operate. The importance ofthis will be appreciated when it is understood that dentists impressionmaterials which are overheated become sticky, lose body and producediscomfort for the patient. If such materials are under heated, theyfail to register major and minor detail. The parts of the apparatus areall separable, so that it is easy to sterilize and maintain the same ina cleanly state.

I claim:

1. A unitary electrical heater adapted to be removably positioned inopen-topped liquid-receiving receptacles, comprising a casing adapted tobe removably positioned on the top of an associated receptacle and toextend into the latter adjacent to one side thereof, aresistor-containing coil carried by said casing, said coil havingvertical portions disposed on opposite sides of the portion of saidcasing depending into said receptacle and in heat-exchangingrelationship with the Walls of said casing, the lower portion of saidcoil being disposed in a substantially horizontal plane and when theheater is actively positioned immediately above. the bottom of theassociated receptacle, means carried by said casing for removablysupporting the same and said coil from the upper edge portions of theassociated receptacle, a thermostatic switch arranged in the dependingportions of said casing, which depending portions are adapted to beimmersed, in liquid contained in the receptacle, conductors uniting saidswitch with the resistors of said coil, manually operated meansaccessible exteric-rly of said casing from the topthereof for,controlling the temperature-responsive action of said switch, anexterior handle disposed parallel to said depending portions andattached to said casing and containing wiring and a socket forelectrically connecting the resistor coil with a current supply, andmeans supporting said receptacle havin a member cooperating with thehandle to permit the entire device to be portable.

2. An electrical heater attachment for opentopped water receptaclescomprising a handle structure adapted to be arranged on the exterior ofa receptacle adjacent to a side wall of the latter, a switch casingjoined with and arranged in parallel relationship with the handlestructure and arranged vertically within the receptacle adjacent to theside wall thereof adjacent to said handle structure, heating tubesconnected with said switch casing, electrical resistors in said tubesfor the generation of heat, a thermostatic switch disposed in saidswitch casing and responsive to the temperature of liquids heated insaid receptacle to open and close an energizing circuit connected withsaid resistors, and an incandescent lamp mounted in said handlestructure and arranged in said circuit to produce a visual signalobservable from the exterior of the handle structure for indicating theclosure of said circuit, and means associated with said receptaclecooperatin with the handle to permit the entire device to be portable.

3. An electrical heater attachment for opentopped water receptaclescomprising a handle structure adapted to be arranged on the exterior ofa receptacle adjacent to a side wall of the latter, a switch casingjoined with and arranged in parallel relationship with the handlestructure and arranged vertically within the receptacle adjacent to theside wall thereof adjacent to said handle structure, heating tubesconnected with said switch casing, electrical resistors in said tubesfor the generation of heat, a thermostatic switch disposed in saidswitch casing and responsive to the temperature of liquids heated insaid receptacle to open and close an energizing circuit connected withsaid resistors, an incandescent lamp mounted in said handle structureand arranged in said circuit to produce a visual signal observable fromthe exterior of the handle structure for indicating the closure of saidcircuit, and horizontally disposed connecting means joining said handlestructure with said switch casing, said means being adapted to rest uponthe upper edge of the receptacle to support the attachment in itsoperating position in association with the receptacle.

4. An electrical heater attachment for opentopped Water receptaclescomprising a handle structure adapted to be arranged on the exterior ofa receptacle adjacent to a side wall of the latter, a switch casingjoined with and arranged in parallel relationship with the handlestructure and arranged vertically within the receptacle adjacent to theside wall thereof adjacent to said handle structure, heating tubesconnected with said switch casing, electrical resistors in said tubesfor the generation of heat, a thermostatic switch disposed in saidswitch casing and responsive to the temperature of liquids heated insaid receptacle to open and close an energizing circuit connected withsaid resistors, an incandescent lamp mounted in said handle structureand arranged in said circuit to produce a visual signal observable fromthe exterior of the handle structure for indicating the closure of saidcircuit, and manually adjustable means accessible from the exterior ofsaid casing for varying the response of said thermostatic switch todiirerent temperature conditions within the receptacle, and meansassociated with said receptacle cooperating with the handle to permitthe entire device to be portable.

5. A portable electric heating device including a receptacle, a heatingelement located in the receptacle adapted to be energized by an electriccurrent, a thermostatic switch mechanism in said receptacle and mountedadjacent to and in heat conducting relationship with said heatingelement, said switch mechanism comprising a tubular metallic casingcontaining a pair of bowed metallic strips therein having a differentcoefficient of expansion than the metal of the tubular casing, saidcasing defining one element of a bimetallic thermostat, said stripsbeing provided with contact means to make and break the electricalcircuit providing current for energizing the heating element, and meansfor placing into and removing from the receptacle the heating elementand the switch mechanism as a unit, said means having a hollow handleportion which houses an incandescent lamp and electrical connections andfacilitates portability of the device.

6. The structure set forth in claim 3 having manually adjustable meansaccessible from the exterior of the casing for varyin the response ofthe thermostatic switch to different temperature conditions within thereceptacle.

'7. The structure set forth in claim 5 having manually adjustable meansaccessible from the exterior of the receptacle for varying the responseof the thermostatic switch to different temperature conditions withinthe receptacle.

HAROLD P. CHAPMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,994,909 Ehrgott Mar. 19, 19352,134,675 Shroyer Oct. 25, 1938 2,194,820 Connell et al Mar. 26, 1940

